I. Process Flow
II. Material Supply and Precautions
Product ordering should select manufacturers certified by the original two ministries. Equipment ordering should be scheduled to arrive when installation conditions are met. After equipment arrives at the site, it should be stored in the on-site equipment warehouse. Invite the owner to jointly conduct an unpacking inspection. The manufacturer's technical documents should be complete, the model and specifications should meet the design requirements, and accessories and spare parts should be complete. The cabinet exterior should be free of damage and deformation, with intact paint. The internal electrical devices, components, and insulating porcelain parts should be complete, without damage, cracks, or other defects.
III. Pre-Installation Preparation
Before installation, verify whether the following civil works have been completed:
(1) Whether the roof and floor slabs have been constructed, and whether there is any leakage on the roof or ground;
(2) Whether the interior decoration works of the distribution room and equipment room have been fully completed;
(3) Whether all types of embedded parts have been installed and meet the equipment installation conditions;
(4) Whether the doors and windows of the room have been installed;
(5) Whether all other processes that cannot be carried out after equipment installation begins have been completed.
When installing high and low voltage cabinets, use a forklift to transport them along the basement level one vehicle ramp to the nearest distance to the power distribution room, then switch to manual chain hoist for transfer. Power cabinets can be moved by manual labor. During transportation, they must be firmly fixed to prevent uneven force, cabinet deformation, or damage to components.
V. Fabrication and Installation of Foundation Steel
According to the drawings, cabinets are arranged in rows and installed on foundation steel. The distribution room uses channel steel of size 10. During fabrication, first straighten and level the bent channel steel, then prefabricate and process the foundation steel according to the drawings, and perform rust removal. After the foundation steel is fabricated, embed it in coordination with civil works according to the positions indicated in the drawings.
When installing the foundation channel steel, use a spirit level to level and align. The unevenness and levelness of the foundation channel steel installation should be less than 1mm per meter and less than 5mm for the total length.
The embedded foundation channel steel for distribution cabinets should be properly grounded. According to design requirements, the grounding flat steel should be welded at both ends to the grounding grid, with the welding surface being twice the width of the flat steel.
When installing cabinets on the channel steel, use 0.5mm iron shims for adjustment between the cabinet and the channel steel during alignment, but no more than 3 shims per location. After leveling and alignment, the panel surfaces should be consistent and arranged neatly. The cabinets and side baffles should be tightened with bolts, and the gaps between cabinets should be less than 2mm
The grounding of the cabinets should be firm and reliable. Each cabinet should be separately connected to the foundation steel for grounding. Weld a terminal lug on the side of the foundation steel at the lower left rear of each cabinet, and connect it firmly with a copper conductor of not less than 6mm2 to the grounding terminal on the cabinet.
Busbars are used for connections between cabinets. Busbar straightening, cutting, processing, installation, painting, and oiling should all comply with specification requirements.
After the distribution cabinets are in place, they must be fixed with bolts pressed against the foundation channel steel, and direct welding is strictly prohibited. When cabinets are arranged individually or in rows, the verticality, levelness, panel surface deviation, and overall deviation of gaps between cabinets should meet the requirements in the following table:
Serial No. Item Allowable Deviation (mm)
1 Verticality (per meter) <1.5
2 Levelness Top of adjacent two panels <2
Top of row of panels <5
3 Panel surface deviation Edge of adjacent two panels <1
Row of panel surfaces <5
4 Gap between panels <2
In this project, all distribution cabinets are equipped with separate working neutral busbars (N) and protective neutral busbars (PE) to facilitate the connection of working neutral wires and protective neutral wires respectively. The cabinet doors, regardless of whether they have electrical components, must be connected to the PE busbar inside the cabinet using yellow-green two-color flexible wires.
VI. Precautions
Before cabinet installation, pay attention to checking the following points to ensure usage requirements:
(1) Drawers should slide flexibly and lightly, without jamming or collision, and drawers of the same specification should be interchangeable.
(2) The mechanical interlock and electrical interlock devices of the drawers should operate correctly and reliably. The disconnector can only be separated after the circuit breaker is opened.
(3) The center lines of the moving contacts and stationary contacts should be consistent, and the contacts should be in close contact to ensure that large currents passing through the contacts do not overheat. At the same time, the secondary circuit connection plugs between the drawer and the cabinet should maintain good contact.
(4) The contact between the drawer and the cabinet, and between the cabinet and the frame, should be good. The grounding contacts between the drawer and the cabinet should be tight. When the drawer is pushed in, the grounding contacts should close before the main contacts, and the opposite when pulled out.
The ordering and installation of low-voltage distribution cabinets should comprehensively consider the connection with external equipment, such as closed busways and cable trays. The reserved connection copper bars in the cabinet should match the phase sequence of the busway, with consistent phase spacing. The sealing between cables entering the cabinet and the cabinet body should use tower-type rubber sealing rings, and the cables should be firmly fixed before entering the cabinet to prevent gravity from damaging the copper bars and electrical accessories inside the cabinet.
During the installation of busbar electrical devices in the cabinet, the electrical clearance between exposed live parts of different phases and between exposed live parts and non-insulated metal frames should not be less than 20mm. If this requirement cannot be met, insulation protection measures must be taken.
VII. Testing and Adjustment:
(1) Test contents: high-voltage cabinet frames, busbars, lightning arresters, high-voltage porcelain insulators, voltage transformers, current transformers, high-voltage circuit breakers, etc.
(2) Adjustment contents: adjustment of overcurrent relays, time relays, signal relays, and mechanical interlock adjustment.
(3) Insulation measurement: use a 500V megger to test the resistance of each circuit at the terminal block, and the value must be greater than 0.5 megohms.
(4) If the secondary circuit has transistors, integrated circuits, or electronic components, the inspection of that part must not use a megger; a multimeter should be used.
(5) Connect temporary control power and operating power, and simulate the actions of control, interlock, operation, relay protection, and signaling respectively.
VIII. Power Transmission Operation and Acceptance
(1) Close the switch of the high-voltage incoming cabinet and check whether the voltage on the voltage transformer cabinet is normal.
(2) Close the switch of the transformer cabinet and check whether the transformer is energized.
(3) Close the switch of the low-voltage incoming cabinet and check whether the three-phase voltage on the voltmeter is normal.
(4) After no-load operation for 24 hours without abnormalities, the acceptance procedures can be processed.
